1. Field of Invention
The present invention relates to incandescent lighting systems operative to provide general lighting at a particularly high luminous efficacy.
2. Prior Art
Previous efforts at achieving significantly improved luminous efficacies in incandescent lighting systems have been principally directed toward providing 120 Volt incandescent light bulbs of higher luminous efficacies.
Efforts of this nature have mainly focused on providing a light bulb having means operative to reflect infrared radiation back onto the incandescent filament while letting visible light escape. Examples of such efforts are provided by numerous prior art references, such as the following U.S. Pat. No. 1,342,894 to Bugbee; U.S. Pat. No. 1,425,967 to Hoffman; U.S. Pat. No. 2,859,369 to Williams et al.; U.S. Pat. No. 4,039,878 to Eijkelenboom et al.; U.S. Pat. No. 4,160,929 to Thorington et al.; U.S. Pat. No. 4,283,653 to Brett; U.S. Pat. No. 4,366,407 to Walsh; and U.S. Pat. No. 4,375,605 to Fontana et al.
However, even though the basic principle has been known for decades, and even though the potentially attainable efficacy improvement is on the order of several hundred percent, light bulbs suitable for general lighting and based on this principle of selective reflection of infrared energy are not yet available on the market. The reason for this is apparently connected with difficulties in translating the basic principle into high-volume production of corresponding cost-effective light bulbs.